Field of the Invention and Related Art Statement
The present invention relates to a method of detecting or judging a state of an operation of cutting a rubber sheet having a number of parallel cords embedded therein by moving a cutter in a cutting direction parallel to a direction in which the parallel cords extend.
In case of manufacturing a tire, there is a process of cutting the above mentioned rubber sheet with cords in a direction parallel to the cords to form a belt. In Japanese Kokai Hei 1-141,730, there is described a known method of detecting a goodness or badness of the operation of cutting the rubber sheet with parallel cords. In this known method, a voltage is applied across an electrically conductive cutter and an electrically conductive plate for receiving the rubber sheet. When the cutter is brought into contact with the rubber sheet receiving plate, an electric current flows through the cutter and plate, but when the cutter is separated from the plate so that the electrical conduction between the cutter and the plate is cut-off, the current does not flow. Therefore, by detecting the current, it is possible to detect the state of the cutting operation.
In the known cutting state detecting method explained above, when the cutter rides slightly on a cord and is separated from the sheet receiving plate, is the cut-off condition produced, so that an abnormal signal is erroneously generated which indicates an inferiority of the cutting state. Further, when electrically insulating stains, injures and so on are existent on the surface of the rubber sheet receiving plate, the current is also interrupted and the abnormal signal is erroneously generated.